The pattern refers to a shape of a specific material on a substrate, and for example, just paying attention to a backplate of a plasma display panel shows that an electrode, a partition wall and a fluorescent material each have a complicated pattern. Among these patterns, the conductive pattern refers to a shape of a conductive material on a substrate, and as a material for forming the conductive pattern, a non-fired type photosensitive conductive paste containing a conductive filler is known. A non-fired type photosensitive conductive paste exhibits conductivity as conductive fillers are brought into contact with each other by curing shrinkage in a curing step at a relatively low temperature, so that a conductive pattern can be formed on a film substrate etc. which is poor in heat resistance. For this reason, development has been advanced for fine pitch wirings of touch panels of smart phones and electronic boards (Patent Documents 1 to 5).
A conductive pattern formation process using a photosensitive conductive paste is a process in which a coated film etc. formed from a photosensitive conductive paste is exposed by applying light thereto through a photomask having a desired pattern, whereby a difference in solubility is generated in a developing solution, so that dissolved components are eluted in the developing solution to form a pattern. Thus, the conductive pattern formation process using a photosensitive conductive paste is absolutely required to include a development processing step using a developing solution.
In the developing solution after development processing, insoluble inorganic components and lumps of organic components remain as insoluble components. These insoluble components, i.e. residues are generated in a large amount in, for example, a process for forming a pattern of a partition wall on a plasma display panel backplate. For recycling a developing solution after development processing to subject the developing solution to development processing again, it is necessary to remove residues from the developing solution after development processing in order to prevent contamination of a development object, clogging of a development processing step device, and so on. On the other hand, a photosensitive conductive paste for forming, for example, an electrode pattern contains an expensive metal such as silver, and therefore separation of residues from a developing solution after development processing also has a meaning as resource recovery.
As a method for separating residues from a developing solution after development processing, a method using a filter or a settling tank is known, but the method has various problems such as high replacement frequency of filters, necessity to stop a device at the time of filter replacement, and necessity of a high-capacity settling tank for lowering a flow rate. Therefore, as a method to replace the above-mentioned method, a centrifugal separation method has been developed (Patent Documents 5 and 6).